The present invention relates to a multimedia communication system comprising a plurality of information processing units connected to a network.
With the progress of the wireless LAN technologies including IEEE 802.11b and the inexpensive high-speed access network technologies such as ADSL (Asymmetric Digital Subscriber Line), the service that provides connectivity to the Internet from public spaces such as railway stations and coffee shops is extending. Also, broadbandization of the mobile communications service is extending as the result of commercialization of the third-generation portable telephone. The utilization of these services makes possible the on-line communication with multimedia such as texts, voices and video by connecting to the Internet, at any time or place, using a highly portable terminal such as a laptop personal computer (PC) or a personal digital assistant (PDA).
Under these circumstances, it is considered to become a common practice for a user to use different terminals at different places. For example, a desk-top PC may be used in the office, while a PDA may be the choice in a moving train. On the other hand, the laptop PC may be a popular means for use in public spaces such as a railway station. For the multimedia communication services, therefore, techniques for selecting a receiving terminal of a receiver-user (hereinafter referred to as the receiving user) upon transmission from the user on transmitting side (hereinafter referred to as the transmitting user) become crucial.
A technique for selecting a receiving terminal is described in JP-A-5-227303 for example. According to this technique, terminal groups, priorities of each terminal in the groups and the information as to whether each of communication media (such as texts, voices, video, etc. which are hereinafter collectively referred to as the media) is busy (occupied) or unbusy (unoccupied) are stored in a central control unit connected to a switching unit. Upon arrival of multimedia data to a terminal group, the occupied/unoccupied status of the medium of each terminal of the group is checked in accordance with the priority, and the data is allowed to be received in the case where the designated medium is unoccupied.
In the technique described above, a terminal group can be registered in such a manner that terminals of one user belong to the same group. In this way, the user who uses a plurality of different terminals on different occasions can receive the data by one of his/her terminals with the highest priority. With the conventional technique described above, however, the priority is assigned to each terminal in advance, and therefore the receiving terminal cannot be selected in accordance with the user's dynamic situation. Also, the conventional technique, in which the transmitting user is not informed of a medium that the receiving user can use at a particular time point, may not be able to establish communication between the transmitting user and the receiving terminal which may be occupied.
In view of this, an improved multimedia communication control technique is in demand.